Refactored out most of internal work for summarizing data opening
the door for generating charts from it. A model is introduced
to hold information needed for a summary, Histogram command is
an example of a partial usage. This is the beginning.
Removed implicit arithmetic traits on Value and Primitive to avoid
mixed types panics. The std operations traits can't fail and we
can't guarantee that. We can handle gracefully now since compute_values
was introduced after the parser changes four months ago. The handling
logic should be taken care of either explicitly or in compute_values.
The zero identity trait was also removed (and implementing this forced
us to also implement Add, Mult, etc)
Also: the `math` operations now remove in the output if a given column is not computable:
```
> ls | math sum
──────┬──────────
size │ 150.9 KB
──────┴──────────
```
* Rename `calc` to `math eval` and allow it to optionally take the expression as an argument
* Moved calc tests to math eval
Also added 2 tests and changed 1 test
* Move calc docs to math eval
* add variance (population)
subcommand to math
* impl variance subcommand with spanning errors for invalid types
* add stddev subcommand to math
* rename bytes to filesize
* clippy fix -- use expect instead of unwrap in variance tests
* Update calculate to return a table when Value is a table
* impl mode subcommand for math
* add tests for math mode subcommand
* add table/row tests for math mode subcommand
* fix formatting
* Add math median example and unit tests
* Update output of other all math ls command examples to keep consistent with math median output
* Fix output of math max example
* Update output of other math commands using pwd examples to keep data consistent
* Adding math docs
* Add some comments to calculate
* Remove redudant message
Message already shows up in subcommands list
* Added not working example
Accidentantly
* Remove table
* Converting average.rs to math.rs
* Making some progress towards math
Examples and unit tests failing, also think I found a bug with passing in strings
* Fix typos
* Found issue with negative numbers
* Add some comments
* Split commands like in split and str_ but do not register?
* register commands in cli
* Address clippy warnings
* Fix bad examples
* Make the example failure message more helpful
* Replace unwraps
* Use compare_values to avoid coercion issues
* Remove unneeded code
